Biology subjects

Ellebedy, A.

Publications and source records attributed to Ellebedy, A..

7 recordsLinked to original sources

bioRxiv2024

mRNA-based influenza vaccine expands breadth of B cell response in humans

Summary paragraphEliciting broad and durable antibody responses against rapidly evolving pathogens like influenza viruses remains a formidable challenge1,2. The germinal center (GC) reaction enables the immune system to generate broad, high-affinity, and durable antibody responses to vaccination3-5. mRNA-based severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines induce persistent GC B cell responses in humans6-9. Whether an mRNA-based influenza vaccine could induce a superior GC response in humans compared to the conventional inactivated influenza virus vaccine remains unclear. We assessed B cell responses in peripheral blood and draining lymph nodes in cohorts receiving the inactivated or mRNA-based quadrivalent seasonal influenza vaccine. Participants receiving the mRNA-based vaccine produced more robust plasmablast responses and higher antibody titers to H1N1 and H3N2 influenza A viruses and comparable antibody titers against influenza B virus strains. Importantly, mRNA-based vaccination stimulated robust recall B cell responses characterized by sustained GC reactions that lasted at least 26 weeks post-vaccination in three of six participants analyzed. In addition to promoting the maturation of responding B cell clones, these sustained GC reactions resulted in enhanced engagement of low-frequency pre-existing memory B cells, expanding the landscape of vaccine-elicited B cell clones. This translated to expansion of the serological repertoire and increased breadth of serum antibody responses. These findings reveal an important role for the induction of persistent GC responses to influenza vaccination in humans to broaden the repertoire of vaccine-induced antibodies.

immunology↗

bioRxiv2024

Repeat modules and N-linked glycans define structure and antigenicity of a critical enterotoxigenic E. coli adhesin

Enterotoxigenic Escherichia coli (ETEC) cause hundreds of millions of cases of infectious diarrhea annually, predominantly in children from low-middle income regions. Notably, in children, as well as human volunteers challenged with ETEC, diarrheal severity is significantly increased severity in blood group A (bgA) individuals. EtpA, is a secreted glycoprotein adhesin that functions as a blood group A lectin to promote critical interactions between ETEC and blood group A glycans on intestinal epithelia for effective bacterial adhesion and toxin delivery. EtpA is highly immunogenic resulting in robust antibody responses following natural infection and experimental challenge of human volunteers with ETEC. To understand how EtpA directs ETEC-blood group A interactions and stimulates adaptive immunity, we mutated EtpA, mapped its glycosylation by mass-spectrometry (MS), isolated polyclonal (pAbs) and monoclonal antibodies (mAbs) from vaccinated mice and ETEC-infected human volunteers, and determined structures of antibody-EtpA complexes by cryo-electron microscopy. Both bgA and mAbs that inhibited EtpA-bgA interactions and ETEC adhesion, bound to the C-terminal repeat domain highlighting this region as crucial for ETEC pathogen-host interaction. MS analysis uncovered extensive and heterogeneous N-linked glycosylation of EtpA and cryo-EM structures revealed that mAbs directly engage these unique glycan containing epitopes. Finally, electron microscopy-based polyclonal epitope mapping revealed antibodies targeting numerous distinct epitopes on N and C-terminal domains, suggesting that EtpA vaccination generates responses against neutralizing and decoy regions of the molecule. Collectively, we anticipate that these data will inform our general understanding of pathogen-host glycan interactions and adaptive immunity relevant to rational vaccine subunit design. Author summaryEnterotoxigenic E. coli (ETEC), a leading cause of diarrhea disproportionately affecting young children in low-income regions, are a priority for vaccine development. Individuals possessing A blood-type are more susceptible to severe cholera-like disease. EtpA, a secreted, immunogenic, blood group A binding protein, is a current vaccine target antigen. Here, we determined the atomic structure of EtpA in complex with protective as well as non-protective monoclonal antibodies targeting two different domains of the protein, allowing us to pinpoint key regions involved in blood-group A antigen recognition and uncover the mechanism of antibody-based protection. In addition, we show through mass-spectrometry that EtpA is extensively and heterogeneously glycosylated at surface-exposed asparagine residues by a promiscuous and low-fidelity glycosyltransferase, EtpC, and that this unique form of bacterial glycosylation is critical for to development of protective immune responses. Lastly, polyclonal antibodies from vaccinated mice as well as monoclonal antibodies obtained from ETEC-infected human volunteers revealed that the highly antigenic surface of EtpA exhibits both protective and non-protective epitopes. These results greatly expand our understanding of ETEC pathogenesis, and the immune responses elicited by these common infections, providing valuable information to aid in the rational design and testing of subunit vaccines.

microbiology↗

bioRxiv2024

Protective effect and molecular mechanisms of human non-neutralizing cross-reactive spike antibodies elicited by SARS-CoV-2 mRNA vaccination

Neutralizing antibodies correlate with protection against SARS-CoV-2. Recent studies, however, show that binding antibody titers, in the absence of robust neutralizing activity, also correlate with protection from disease progression. Non-neutralizing antibodies cannot directly protect from infection but may recruit effector cells thus contribute to the clearance of infected cells. Also, they often bind conserved epitopes across multiple variants. We characterized 42 human mAbs from COVID-19 vaccinated individuals. Most of these antibodies exhibited no neutralizing activity in vitro but several non-neutralizing antibodies protected against lethal challenge with SARS-CoV-2 in different animal models. A subset of those mAbs showed a clear dependence on Fc-mediated effector functions. We determined the structures of three non-neutralizing antibodies with two targeting the RBD, and one that targeting the SD1 region. Our data confirms the real-world observation in humans that non-neutralizing antibodies to SARS-CoV-2 can be protective.

immunology↗

bioRxiv2023

Spatiotemporal development of the human T follicular helper cell response to Influenza vaccination

We profiled blood and draining lymph node (LN) samples from human volunteers after influenza vaccination over two years to define evolution in the T follicular helper cell (TFH) response. We show LN TFH cells expanded in a clonal-manner during the first two weeks after vaccination and persisted within the LN for up to six months. LN and circulating TFH (cTFH) clonotypes overlapped but had distinct kinetics. LN TFH cell phenotypes were heterogeneous and mutable, first differentiating into pre-TFH during the month after vaccination before maturing into GC and IL-10+ TFH cells. TFH expansion, upregulation of glucose metabolism, and redifferentiation into GC TFH cells occurred with faster kinetics after re-vaccination in the second year. We identified several influenza-specific TFH clonal lineages, including multiple responses targeting internal influenza proteins, and show each TFH state is attainable within a lineage. This study demonstrates that human TFH cells form a durable and dynamic multi-tissue network.

immunology↗

bioRxiv2021

SARS-CoV-2 mRNA vaccination elicits robust and persistent T follicular helper cell response in humans

SARS-CoV-2 mRNA vaccines induce robust anti-spike (S) antibody and CD4+ T cell responses. It is not yet clear whether vaccine-induced follicular helper CD4+ T (TFH) cell responses contribute to this outstanding immunogenicity. Using fine needle aspiration of draining axillary lymph nodes from individuals who received the BNT162b2 mRNA vaccine, we show that frequency of TFH correlates with that of S-binding germinal center B cells. Mining of the responding TFH T cell receptor repertoire revealed a strikingly immunodominant HLADPB1* 04-restricted response to S167-180 in individuals with this allele, which is among the most common HLA alleles in humans. Paired blood and lymph node specimens show that while circulating S-specific TFH cells peak one week after the second immunization, S-specific TFH persist at nearly constant frequencies for at least six months. Collectively, our results underscore the key role that robust TFH cell responses play in establishing long-term immunity by this efficacious human vaccine.

immunology↗

bioRxiv2021

Structure of a germline-like human antibody defines a neutralizing epitope on the SARS-CoV-2 spike NTD

Structural characterization of infection- and vaccination-elicited antibodies in complex with antigen provides insight into the evolutionary arms race between the host and the pathogen and informs rational vaccine immunogen design. We isolated a germline-like monoclonal antibody (mAb) from plasmablasts activated upon mRNA vaccination against SARS-CoV-2 and determined its structure in complex with the spike glycoprotein by cryo-EM. We show that the mAb engages a previously uncharacterized neutralizing epitope on the spike N-terminal domain (NTD). The high-resolution structure reveals details of the intermolecular interactions and shows that the mAb inserts its HCDR3 loop into a hydrophobic NTD cavity previously shown to bind a heme metabolite, biliverdin. We demonstrate direct competition with biliverdin and that - because of the conserved nature of the epitope - the mAb maintains binding to viral variants B.1.1.7 and B.1.351. Our study illustrates the feasibility of targeting the NTD to achieve broad neutralization against SARS-CoV-2 variants.

immunology↗

bioRxiv2021

Functionality of the putative surface glycoproteins of the Wuhan spiny eel influenza virus

A panel of novel influenza-like virus sequences were recently documented in jawless fish, ray-finned fish, and amphibians. Of these, the Wuhan spiny eel influenza virus (WSEIV) was found to phylogenetically cluster with influenza B viruses as a sister clade. Influenza B viruses have been historically documented to circulate only in humans, with certain virus isolates found in harbor seals. It is therefore interesting that a similar virus was potentially found in fish. Here we characterized the functionality and antigenicity of the putative hemagglutinin (HA) and neuraminidase (NA) surface glycoproteins of the WSEIV to better understand this virus and its pandemic potential. Upon functional characterization of NA, we identified that the WSEIV NA-like protein has sialidase activity comparable to B/Malaysia/2506/2004 influenza B virus NA, making it a bona fide neuraminidase that could be inhibited by NA inhibitors. Testing of the functionality of HA was carried out including receptor specificity, stability, and preferential airway protease cleavage and showed very specific binding to monosialic ganglioside 2 (GM2). To probe the degree of conservation of target epitopes, binding of known broadly cross-reactive monoclonal antibodies targeting the influenza B HA and NA, respectively, were assessed through enzyme linked immunosorbent assays against recombinant WSEIV glycoproteins. Human serum samples of patients with antibodies to influenza B viruses were used to determine the cross-reactivity against these novel glycoproteins. Very few monoclonal antibodies - notably including pan NA antibody 1G01 - showed cross-reactivity and reactivity from human sera was basically absent. In summary, we have conducted a functional and antigenic characterization of the glycoproteins of the novel WSEIV to assess if it is indeed a bona fide influenza virus potentially circulating in ray-finned fish.

microbiology↗